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CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    Consider the following statements.
    I. \[La{{(OH)}_{3}}\]is the least basic among hydroxides of lanthanides.
    II. \[Z{{r}^{4+}}\]and\[H{{f}^{4+}}\]possess almost the same ionic radii.
    III. \[C{{e}^{4+}}\]can act as an oxidizing agent.
    Which of the above is/are true?

    A)  (I) and (III)       

    B)  (II) and (III)

    C)  (II) Only          

    D)         (I) and (II)

    E)  (I)-only

    Correct Answer: B

    Solution :

    I. The basic character of hydroxides decreases from\[La{{(OH)}_{3}}\]to\[Lu{{(OH)}_{3}}\].Thus\[La{{(OH)}_{3}}\]is the most basic among lanthanoid hydroxides.
    II. \[Z{{r}^{4+}}\]and\[H{{f}^{4+}}\]is almost similar in size due to lanthanide contraction.
    III. Cerium exhibits +4 oxidation state in aqueous solution and possesses the tendency to attain +3 oxidation state.
    Therefore\[C{{e}^{4+}}\]is a good oxidizing agent. \[\underset{oxidant}{\mathop{C{{e}^{4+}}}}\,+F{{e}^{2+}}\xrightarrow{{}}C{{e}^{3+}}+F{{e}^{3+}}\]


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